topic Re: How to get variables into Python code block of arcpy.management.CalculateField in ArcGIS API for Python Questions

How to get variables into Python code block of arcpy.management.CalculateField

TomGeo — Thu, 01 Dec 2022 14:48:07 GMT

I have one calculation where it works great getting a variable in:

arcpy.management.CalculateField(sector_angle, 'Buffer', "getBuffer(!Area!)", "PYTHON3", f"""def getBuffer(area): if area < {median_area}: return 1 if area > {median_area}: return 2""", "TEXT", "NO_ENFORCE_DOMAINS")

And I have another calculation on the same feature class where it does not work.

arcpy.management.CalculateField(sector_angle, 'Buffer_Radius', "setDistance(!Buffer!)", "PYTHON3", f"""def setDistance(buffer): if buffer == 1: return {pnt[2]} elif buffer == 2: return {pnt[3]}""", "FLOAT")

Some example on how the variables look:

pnt[2] = 2043.8900146484375

pnt[3] = 4087.780029296875

The type of both variables is float, but the resulting 'Buffer_Radius' field contains only NaN.

I tried all sorts of stuff on how to get the variables into the code block, but while it was so easy in the first function, I don't have luck with the second one. How do I get my variables into the 'Buffer_radius' field?

Re: How to get variables into Python code block of arcpy.management.CalculateField

DanPatterson — Thu, 01 Dec 2022 17:38:58 GMT

pnt[2]

can't be a variable it is a slice of pnt, so where is pnt defined? and maybe if it is somewhere try

p2 = pnt[2]

p3 = pnt[3]

assuming of course that the values are slices of pnt

Re: How to get variables into Python code block of arcpy.management.CalculateField

RogerDunnGIS — Thu, 01 Dec 2022 20:03:17 GMT

I think it has to do with the properties of the buffer_radius field. Maybe there's something amiss with regards to scale and precision that won't let numbers like 2043.8900146484375 and 4087.780029296875 fit inside it. Or, if buffer_radius is a text field, maybe it's not long enough. What can you tell us about that field?

Re: How to get variables into Python code block of arcpy.management.CalculateField

DavidAnderson_1701 — Thu, 01 Dec 2022 22:22:32 GMT

Throwing a few thoughts out here. How about using a lambda function? Also I wonder about the use of the {}. In't that the syntax for defining a dictionary? I think the NAN might be because the return value is a NULL dictionary.

Re: How to get variables into Python code block of arcpy.management.CalculateField

DanPatterson — Fri, 02 Dec 2022 00:19:12 GMT

{} is also used in python format strings.

median_area = 5 area = 2 func = f""" def getBuffer(area): if area < {median_area}: return 1 if area > {median_area}: return 2 """ print(func) def getBuffer(area): if area < 5: return 1 if area > 5: return 2

Re: How to get variables into Python code block of arcpy.management.CalculateField

TomGeo — Fri, 02 Dec 2022 09:02:36 GMT

Thanks for all the valuable thoughts and inputs. In the end, since I had all the logic anyway in Python, I ended up using an update cursor. Time wise, it is almost the same if I run those two CalculateField runs, slightly slower...

I tried the whole thing of course straight in ArcGIS Pro and there my code block works. However, I think @RogerDunnGIS has a fair point talking about the format of fields. The first CalculateField run is creating the buffer field, as 'TEXT'! But my second CalculateField run is using integers in the if-statement...

I haven't had time to try it, but 1 should not be '1', and thereby the error source is once more found about 40 cm in front of the screen. 😅